Association and In Silico studies of OPRM1 gene missense variant A118G among addicted individuals undergoing methadone treatment in a northern Iranian population

Introduction: The aim of the current study was to investigate the association and in silico analyses of rs1799971(A118) with the occurrence of opioid addiction among northern Iranians for the first time.Methods: Genomic DNAs of 202 healthy and 202 opium-addicted men were extracted from whole bloodsamples through Salting Out procedure. A118G was genotyped by Amplification Refractory Mutation SystemPCR (ARMS-PCR). All analysses were performed by SNPalyze (ver. 8.1 software Dynacon Japan). Homologymodeling was performed and validated by Swiss model, Phyre2, Swiss-PDB-Viewer, RAMPAGE, ProSAsoftwares and docked by Autodock Vina ver. 1.5.6.Results: A significant difference was observed between groups followed dominant hereditary model [P=0.02,OR=0.59; 95CI (0.39-0.91)]. The frequency of AA, AG, and GG carriers were 0.64 and 0.75, 0.29 and 0.16, and0.07 and 0.08 among cases and controls, respectively. In silico analyses of OPRM1 protein at Asn40 (dominantmodel) and Asp40 (recessive model) with R-methadone and S-methadone as ligands revealed that bestcomformation of S-methadone had more binding affinity to Asn40 compared to Asp40 model (binding Energy=-6.44 kcal/mol with 2 Hydrogen bonds formation, and E=-6.26 kcal/mol with no H-bond formation, respectively).Also, R-methadone in recessive model showed better binding affinity (E=-6.55 kcal/mol with 3 H-bondformation) than S-methadone in both Asn40 and Asp40 models.Conclusion: Cosequently, A118G might have a potential association with opioid addiction and S-methadone canaffect Iranians in lower dosages than R-methadone. Based on this, genotyping of rs1799971 may be helpful andmore accurate in methadone treatment and designing new terapeutic drugs.

Keywords:

Opioid addiction , A118G , Association study , Homology modeling , Docking